In one of the most extraordinary geophysical events ever recorded, a colossal tsunami in East Greenland sent seismic vibrations rippling through Earth’s crust for nine continuous days. The slow, rhythmic signal puzzled scientists worldwide until satellite imagery revealed the source: a massive mountainside collapse into a remote Arctic fjord.
The event unfolded without warning in September 2023. Seismic stations from Alaska to Australia began recording an unusual, steady pulse repeating every 92 seconds. Unlike earthquakes, which produce sharp, short-lived tremors, this signal was smooth, persistent, and globally synchronized. No one felt it but the planet did.
Researchers soon traced the disturbance to Dickson Fjord, a narrow inlet along Greenland’s eastern coast, flanked by cliffs rising more than 3,000 feet. Satellite images showed a fresh scar on one mountainside, where an enormous section of rock and ice had vanished.
On September 16, 2023, more than 25 million cubic yards of rock and ice broke loose and thundered into Dickson Fjord. The impact displaced vast amounts of water, generating a mega-tsunami that surged to an estimated height of 650 feet one of the tallest waves ever documented.
The wave raced through the fjord’s two-mile corridor, slammed into a headland, and rebounded repeatedly. Although the area was uninhabited at the time, the force destroyed equipment worth roughly $200,000 at a research station on nearby Ella Island.
Instead of dissipating, the water began oscillating from side to side in a phenomenon known as a seiche. This sloshing motion caused the water surface to rise and fall by tens of feet in a regular rhythm, repeatedly pressing against the seafloor like a giant piston.
This relentless movement was strong enough to deform Earth’s crust ever so slightly, producing the strange seismic signal detected worldwide. Unlike a typical earthquake, which fades quickly, the oscillation barely weakened over more than a week.
Computer models produced varying estimates of the wave height ranging from about 8 feet to as much as 30 feet during the sustained sloshing but all agreed on the cause: a landslide-driven tsunami trapped within the fjord’s geometry.
Simulating such a long-lasting event proved exceptionally difficult. Scientists had to account for the fjord’s shape, depth, and reflective boundaries, which helped sustain the oscillation far longer than expected.
Solving the mystery required a massive collaborative effort involving more than 70 scientists from 41 institutions. Field teams documented fresh scars high on the cliffs, while supercomputers reconstructed the landslide’s trajectory and the fjord’s response in fine detail.
Researchers combined geological surveys, seismic data, satellite observations, and fluid dynamics models to piece together the full sequence of events. Only through this interdisciplinary approach did the unusual seismic signal finally make sense.
Climate change and growing Arctic risks
Scientists say climate change played a crucial role. Glaciers that once stabilized the mountain slope had thinned significantly due to warming air and ocean temperatures, removing the natural support that kept the rock face intact.
Similar conditions triggered a deadly tsunami in Greenland’s Karrat Fjord in 2017, which destroyed homes and claimed lives. While Dickson Fjord is remote, it lies near cruise ship routes, raising concerns about growing risks as Arctic tourism and shipping expand.
Authorities are now evaluating early-warning systems that combine satellite monitoring with real-time seismic data to detect future slope failures before waves are generated.
A key breakthrough came from the Surface Water and Ocean Topography (SWOT) satellite, launched in late 2022. Unlike older satellites that measure only narrow strips of water, SWOT maps wide swaths with high resolution, allowing scientists to observe subtle changes in sea surface height even in narrow fjords.
This capability enabled researchers to directly observe the lingering wave motion weeks after the landslide occurred—something previously impossible in such remote regions.
The findings demonstrate how next-generation satellites are transforming scientists’ ability to study extreme ocean events, including tsunamis, storm surges, and rogue waves, especially in places where traditional instruments are sparse or nonexistent.
Researchers are now searching historical seismic records for similar slow, rhythmic signals that may point to past disasters that went unnoticed. Each discovery improves models of how landslides, fjord geometry, and water depth interact to amplify extreme waves.
The event is a stark reminder that even Earth’s quietest corners can unleash planet-scale signals. As warming continues to destabilize polar landscapes, scientists say the need to monitor, understand, and anticipate these rare but powerful events has never been greater.
Sometimes, the planet speaks softly but for nine days, this time, it spoke to the entire world.